What is the external area of a rectangular box of length 6cm breadth 4cm and height 4cm?

Assuming external area is the surface area.
2 x 6 x 4 = 48 sq cm (top and bottom area)
2 x 6 x 4 = 48 sq cm (two sides)
2 x 4 x 4 = 16 sq cm (two ends)

48 + 48 + 16 = 112 square centimetres is the total surface area.